As discussed in U.S. Pat. No. 4,024,093 (Abolins et al.), ferric salts such as ferric stearate can be employed in combination with a halogenated aromatic compound such as hexabromobiphenyl to impart improved flame retardant properties to the polyphenylene ether blend.
As shown by Japanese Patent J59-226046 (June 7, 1983), ammonium salts also have been described as effective flame retardants for blends of polyphenylene ether and styrene resins. For example, blends of 50 parts by weight of polyphenylene ether and 50 parts by weight of rubber modified high impact polystyrene were rendered V-O by the addition of 5 parts by weight of ammonium bromide or ammonium chloride. Blends comprised of 30 parts by weight of polyphenylene ether, and 70 parts by weight of high impact polystyrene requires 10 parts of ammonium bromide to achieve V-O flame-out times.
It would be desirable, therefore, to make flame-retardant blends of polyphenylene ether and polystyrene resin without the employment of a significant amount of polyhalogenated aromatic compounds or excessive amounts of ammonium halides which are difficult to disperse during the processing of blends of polyphenylene ether and polystyrene resin under melt conditions because the ammonium salts are generally of a crystalline nature.
The present invention is based on our discovery that organoamine salts having the formula EQU R.sub.n H.sub.3-n NHX, (1)
have been found to be more readily compatible with the polyphenylene ether blends in the melt and have been found to impart flame retardance to extrudate of such polyphenylene ether blends when incorporated in such blends in effective amounts prior to extrusion, where R is a C.sub.(1-14) monovalent hydrocarbon radical and preferably a C.sub.(1-8) alkyl radical, X is a halogen radical or an organosulfonate radical, and n is an integer having a value of from 1-3 inclusive.
As used hereinafter, the term "extrudate" means polyphenylene ether blend which has been melt extruded in contact with a ferruginous surface.